Because if you actually know anything about biology, it doesn't make any sense as a question.
I would say it's a little more nuanced. What you are is partly determined by nurture and that part could be said to be "designed" if we interpret the word loosely.
So I think the most sensible answer is that if you want to know what a particular human was designed for, you should ask his parents (and to a lesser degree, friends, teachers, etc).
In the future man may become able to genetically engineer the next generation and at that point, man would be designed in a more literal sense.
Pets are bred in a way so far diverged from natural evolution that you could call them "designed" already.
Going by this, man was "designed" by the vagaries of chance and selective pressures in the environment to:
- survive by using cooperation and communication in large numbers
- Alter the environment so as to suit the needs of the group
- Use our relatively large brain to treat practical problems of survival as things that are solvable, and not just reacted to. Allowing for the development of technology
As opposed to other species which are "designed" to survive by virtue of outbreeding stuff that kills them, being difficult to find/kill, being able to kill almost anything else in their specific environs.